Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$47.47	10.241%	$52.3314	$52.33	$52.35	$52.30
Purchase #2	$99.82	11.806%	$111.6047	$111.60	$111.60	$111.60
Purchase #3	$158.35	13.512%	$179.7463	$179.75	$179.75	$179.70
Purchase #4	$226.61	13.377%	$256.9236	$256.92	$256.90	$256.90
Purchase #5	$217.88	6.614%	$232.2906	$232.29	$232.30	$232.30
Purchase #6	$96.51	5.137%	$101.4677	$101.47	$101.45	$101.50
Purchase #7	$106.84	8.607%	$116.0357	$116.04	$116.05	$116.00
7 purchase totals =	$953.48		$1,050.4000	$1,050.40	$1,050.40	$1,050.30